Health authorities in Hong Kong, Singapore, and Tokyo are screening passengers flying in from Wuhan at airports, and the US Centers for Disease Control and Prevention (CDC) is doing so at airports in New York, Los Angeles, San Francisco.

The virus, called 2019-nCoV, was first detected in the city of Wuhan, central China, at the end of 2018. As it is a new strain of coronavirus - which is one that infects the nose, throat, or sinuses - that has not been seen by humans before, scientists are scrambling to understand the treat it.

The World Health Organisation said it will hold a meeting on Wednesday to decide whether to declare "a public health emergency of international concern," and what recommendations to make. It has previously declared such an emergency for swine flu and Ebola.